1. Field of the Invention
The invention is directed to an apparatus for measuring the total content of organic carbon and nitrogen in water by evaporating a specimen taken from the water and oxidizing the organic carbon to form carbon dioxide and the nitrogen to form nitrogen oxide in a thermal reactor. The measurement is carried out on the basis of the gas specimen of carbon dioxide (CO.sub.2) and nitrogen oxide (NO) formed from the specimen. A NDIR gas analyzer is used for the simultaneous measurement of the carbon dioxide and nitrogen oxide gas components, and has two adjacent vessels which are provided with the gas specimen and a comparison gas, respectively, and which are penetrated by modulated light beams from an infrared radiator. The light beams fall on pneumatic receivers arranged subsequent to the vessels after being partially absorbed in the vessels, and the receivers have two chambers arranged one after the other in the radiating direction, each of which is filled with one of the components of the gas specimen to be determined.
2. Description of the Prior Art
The abbreviations listed below are used throughout the application:
TOC (Total Organic Carbon) for the totality of carbon in the form of organic carbons present in the water to be measured; PA1 TN (Total Nitrogen) for the totality of nitrogen present in the water to be measured; PA1 TIC (Total Inorganic Carbon) for the totality of carbon in the form of inorganic compounds present in the water to be measured; PA1 TC (Total Carbon) for the totality of carbon present in the water; PA1 VOC (Volatile Organic Carbon) for the totality of carbon in the form of volatile organic compounds present in the water to be measured.
The organic fraction of carbon TOC is an oxygen-depleter and accordingly important for the analysis of water. The principle for determining the TOC amount is set forth in DIN 38409 (H) Part 3. Often, only a part, i.e. that of the dissolved TOC fraction, is detected in practice instead of the correct value. Volatile organic components which are lost when separating the specimen from inorganic components may also frequently be present in the water. Accordingly, the TOG value is not fully determined.
In addition to the TOC value, the fraction of bonded nitrogen TN is significant in that it allows assertions to be made concerning the loading of the water with nitrogen compounds from natural and industrial emitters. A suggestion for measurement is set forth in the DIN Draft 38 409 Part 27.
TOC analyses are known. TC and TIC are measured and calculated by subtracting TOC; (DE-OS 28 11 135, DE-OS 24 58 143, DE-AS 22 60 295, DE-OS 23 22 293, EP-PS 01 50 923). In isolated cases, an added TN measurement is included in a TOC measurement by providing a corresponding analyzer which is costly and creates undesirable delays in indication (DE-OS 26 21 616). Calibration is frequently effected manually with a high-purity null liquid for adjusting the zero value and with a test solution for sensitivity. Measurement errors based on the principle of measurement are also taken into account and thus there occur deviations from the given sensitivity when the base load of CO.sub.2 changes.